What is it?

If you're new to Synth DIY and have never heard of the SN76477 IC, there's a good reason - it's long been out of production. But it still exists out there in the wild - a few supply houses on the internet still list it, and it's been known to inhabit parts bins all over the world waiting for just the right application.

The SN76477 appeared in many a video game of the late '70s and early '80s, supplying players with bleeps, bloops and swept noise as they vanquished pixellated aliens dropping from the skies. It was also featured in other items, more often than not, toys. There were a few kits out there for hobbyists. Some were music related, others were for just making revving engine, steam engine, explosion and gunshot effects. Somewhere between the mid '80s and early '90s (I'm not sure when) Texas Instruments terminated the SN76477. With prejudice.

The SN76477N didn't deserve such an unceremonious fate; if ever there was a feature packed DIY wet dream, it was the SN76477N. In fact, the SN76477 is a fully loaded synthesizer on a chip. Within its silicon boundaries lie the following functions:

A Voltage Controlled Square Wave Oscillator A Super Low Frequency Oscillator (a fancy term for LFO) A VCA-like 'modulator' A Sweepable Digital Noise Generator (shift register based) A Filter for the Digital Noise Generator An Envelope Generator (Attack/Decay) A programmable Mixer

Why did you make it?

What makes it special?